Dielectric heating device for the edge gluing



Get. 25, 1955 w. RUEGGEBERG 2,721,924

DIELECTRIC HEATING DEVICE FOR THE EDGE GLUING Filed April 17, 1952 4Sheets-Sheet 1 IN VENTOR WERNER RUEGGEBERG ATTORNEY Oct. 25, 1955 w.RUEGGEBERG 2,721,924

DIELECTRIC HEATING DEVICE FOR THE EDGE GLUING Filed April 17, 1952 4Sheets-Sheet 2 INVENTOR WERNER RUEC-GEBERG ATTORNEY Oct. 25, 1955 w.RUEGGEBERG 2,721,924

DIELECTRIC HEATING DEVICE FOR THE EDGE GLUING Filed April 17, 1952 4Sheets-Sheet 3 I INVENTOR 45 7 l 5 WERNER RUEGGEBERG ATTORNEY Oct. 25,1955 w. RUEGGEBERG 2,721,924

DIELECTRIC HEATING DEVICE FOR THE EDGE GLUING Filed April 17, 1952 4Sheets-Sheet 4 INVENTOR WERNER RUEGGEBERG ATTORNEY DIELECTRIC HEATINGDEVICE FOR THE EDGE GLUING Werner Rueggeberg, Lancaster, Pa., assignorto Armstrong Cork Company, Lancaster, Pa., a corporation of PennsylvaniaApplication April 17, 1952, Serial No. 282,750

Claims. (Cl. 21910.45)

This invention relates to a dielectric heating device for edge gluingand is concerned particularly with a device for edge gluing pieces ofcork composition, for instance, in the manufacture of gaskets. Gasketsare generally formed by dieing a single piece from a sheet of corkcomposition. This leaves a center portion of scrap which in a crankcasegasket, for example, may be of greater volume than the actual gasket.Frames of cork composition of the general outline of the gasket to beformed have been made of glued-up blocks, and these frames have beensliced into gasket blanks from which the gaskets have been died out.

With the apparatus of the present invention, gasket segments may besevered from sheets of the desired thickness without substantial scraploss and the segments adhesively joined together to produce a finalgasket of the desired shape and thickness Without further fabrication.

It is an object of this invention to provide an edgegluing device inwhich an electrode may be reciprocated from an inoperative position toan operative position. embracing a workpiece and in which such motionmay be utilized to closely couple the movable electrode to ahighfrequency source.

Another object of the invention is to provide an edgegluing device whichwill simultaneously form a plurality of heat-activated adhesive joints,such as in the joining f of two side pieces to an end segment in theformation of a gasket, with the activation being effected by dielectricheating, employing spaced pairs of electrodes constituting part of asymmetrical high-frequency system.

A further object of the invention is to provide a dielectric heatingdevice for edge gluing in which a separate capacitive current returnpath to the oscillator is provided, thus affording a reliablehigh-frequency switching system free of mechanical contacts.

An additional object of this invention is to provide a dielectricheating device in which one of an electrode pair is capacitively coupledto the high-frequency source, with the impedance of the coupling beingsubstantially less than the impedance of the load to assure developmentof nearly all available generator voltage in the workpiece undertreatment.

Other objects of the invention will be apparent from consideration of atypical embodiment of the invention which will be described inconjunction with the accompanying drawing, in which:

trode' assembly;'and

Figure 7 is a view similar to Figures 5 and 6 showing upper and lowerelectrode assemblies and an air switch constituting part of thecapacitive current return path to the oscillator referred to previously.

While a gasket-segmenting device has been chosen for illustration of theinvention, it will be understood that the device will be useful in edgegluing generally.

The general arrangement The general arrangement shown in Figure 1includes a pair of upper electrode assemblies 2 and 3, a pair of lowerelectrode assemblies 4 and 5, a source of high-frequency power 6connected to said electrodes through coaxial cables 7 and 8, and a pairof unique air switches 9 and 10. Tuning stubs 11 and 12 are provided foradjusting the individual left and right electrode sets to proper tuning.The upper electrode sets are mounted for vertical reciprocation towardand away from the lower electrode sets; and, in the embodimentillustrated, this is efiected by an air cylinder and piston arrangement13. A workpiece-supporting table 14 and a lower mounting table 15 arepositioned upon a framework 16 which is preferably arranged so that amachine operator may sit in front of the machine and feed the workpiecesthereto.

The upper electrode assemblies Each upper electrode assembly (Figure 5)includes a metal strip electrode 17 which is received within apolystyrene facing member 18. The facing member is secured to a backingor supporting member 19 of fabric-reinforced insulating material such asMicarta. A lead connector 20 is received within a threaded opening inelectrode strip 17, passes through supporting member 19 and a bushing21. A flat metal lead 22 is secured to the connector 29 and to a plate23, forming part of an associated air switch. A screw 24 passes throughthe plate 23 and is received within the supporting member 19, attachingthe plate 23 in fixed position with respect to the electrode structure.

A crosshead 25 (Figure 3) of electrical insulation material connects thetwo electrode assemblies 2 and 3 through electrically insulatingmounting blocks 26 and 27 and metal mounting brackets 28 and 29. Thecrosshead 25 is adjustably mounted on a T-shaped head support 30 byscrews 31, 32, and 33 which pass through slotted openings in thecrosshead 25. The head support 30 is secured to the air cylinder andpiston arrangement 13 (Figure 1) which imparts a vertical reciprocatorymovement to the electrode assemblies as will be more fully hereinafterdescribed.

There is no direct electrical connection, i. e., no mechanicalconnection, between the electrodes 17 and the high-frequency source and,therefore, no substantial problem of maintaining reliable and consistentcircuit completion is encountered.

The lower electrode assemblies Each lower electrode assembly (Figure 6)includes a metal strip electrode 34 which is preferably complementary tothe cooperating upper electrode 17 and is also received within apolystyrene facing member 35. A backup 36 of Teflon insulation or othermaterial having the requisite dielectric properties for this service isprovided for the electrode strip. Below this is positioned a backing orsupporting member 37 of Micarta. A Micarta spacing plate 38 is disposedbelow the member 37 and screws 39 (Figure 3) which pass through members36 and 37, and bushings 49 are received within tapped openings inspacing plate 38. The spacing 0 plate is in turn supported by a metalconnecting plate 41 to which it is secured by screws 42 which passthrough bushings 43 and are received within connecting plate 'solderingthe plate 48 to the connecting plate 41.

41. The metal connecting plate 41 is disposed above lower mounting tableHand is secured thereto by screws 44 which pass through bushings 45 andare received within threaded openings in the lower mounting table. Anouter shielding tube 46 of the coaxial conductor associated with theelectrode assembly is electrically connected to the connecting plate 41by soldering. The electrode 34 is connected to the high-frequency sourcethrough a rod 47 which passes through the shielding tube '46 of thecoaxial conductor. The rod 47 is received within a threaded openingprovided in the electrode strip 34. The spacing plate 38 serves tostagger the fastenings which connect the members 3437 and plate 41 andprovides a more effective insulation of the high potential electrodestrip '34 from ground, the connecting plate 41 being at ground potentialand electrode strip'54 at maximum potential above'ground.

The air switches Each of the air switches 9 and (Figure 7) is formed ofmetal plates 48 and 49 which are connected together by screws which passthrough plate 48 and bushing 56 and are received within threadedopenings in plate 49. The assembly is held in fixed position by Sinceplates' tti and 49 are electrically connected to one another and toplate 41 which is in turn electrically connected to shielding tube '46which constitutes the grounded leg of the high-frequency source, whenplate 23 which is electrically connected to the upper electrode 17 isdisposed 9 between plates 48-and 49, the electrode 17 is capacitivelycoupled to the high-frequency source at essentially ground potential.The plates 48 and 49 are of extensive surface area and are spaced asclosely together as reasonably possible to receive plate 23 therebetweenwithout actual physical contact. If is desirable to keep the voltageloss to as low a value as possible. Eifective capacitive coupling isefiected when the upper electrodes have been brought 'to a positionoverlying and in tangential contact with a workpiece disposed betweenthe upper and lower electrodes. The capacity of the air switches 9 and'10 is substantially greater than the capacity of the load disposedbetween the electrodes 17 and'34, assuringthe development of nearly allavailable generator voltage in the workpiece under treatment. The straycapacitance between the high potential electrode 3'4 and the plates ofthe air switches 9 and 10, as well as the other elements of the groundedleg of thesystem, is so small as to have no substantial efiect on theoperation of the system. Stated in other words, the impedance of the airswitch system is negligible, and essentially all of the generatorvoltage is applied to the workpiece which constitutes the load.

Suitable guarding may be provided to protect'the machine operator frominjury by the reciprocating plates 23. In the embodiment illustrated inFigure 3, each of the guards includes an upright panel 52 of insulationThe coaxial cables 7 and 8 (Figure 1) originate at the oscillator 6 andextend through junction boxes 6t 64 and then, as shown in Figure 6, areconnected to the lower electrode strips 34 and connecting plates 41. Inorder to obtain a symmetrical system, the coaxial cable extends tojunction box 62 which is disposed midway between the electrodeassemblies, entering fat the rear of the box (Figure 2) and thenbranching out in opposite directions to junction boxes 63 and 64 (Figure1). A hollow copper tube and brass rod coaxial line as shown in Figures6 and 7 may be used, but other efiiective coaxial cable arrangements maybe substituted.

The tuning stubs 11 and 12 (Figure I) serve to balance the right andleft electrode sets for equal voltage and also to so adjust theimpedance value that 'the re sultant impedance at the oscillator outputcan be tuned for eflicient load matching with a tuning stub 65 whichprojects from junction box 60. A variable loop coupler may be providedwithin the oscillator 6 to furnish final coupling adjustment to theoutput of the oscillator. Such coupling'is generally conventional, andthe details of the tuning stubs is not of critical importance. They maybe simply constructed as shown in section in the lower left-hand portionof Figure 1 where tube 66 of tuning stub 11 is received within junctionbox 64 and soldered thereto. The tube 66 receives a tuning member 67which may be in the form of a brass cylinder which fits within the wallof the tube 66 and is movable to adjusted position therein. The .tuningmember 67 is drilled and tapped throughout its length and is received ona threaded supporting rod 68 which extends throughout the length of thetube '66 and is anchored in the junction box 64 but insulated therefrom,preferably by connection of supporting rod 68 to the rod 47 (Figure 6)of the lower electrode assembly. The tuning member 67 may be adjusted byproviding a projection 69 thereon which may be engaged by a hollowadjusting wrench inserted into the tube 66 from the lower end thereof. Acover cap 70 is preferably provided over the end of the tube 66 and maybe held in place by a nut 71 threaded onto rod 68. The cover cap 70 isremoved when the tuning member '67 is to be adjusted.

The crosshead actuating assembly The crosshead actuating mechanismincludes the air cylinder and piston 13, the piston rod 76 of which isconnected to actuating rod 72 of the crosshead by an offset connection77. The air cylinder 13 is supplied with air from a source S, and theapplication of air to the air cylinder and'piston 13 is controlled inproper timed relationship with the application of the high-frequencyfield to-the workpiece. Any suitable equipment may be provided tocontrol the operation of the air cylinder and piston arrangement 13 andthe high-frequency oscillator in proper sequence, and limit switches 78,79, and 80 which areshown in Figure 1 may form part of the controlsystem. Such systems are conventional and will vary with the type ofworkpiece to be operated upon,

the time interval required for positioning the pieces to be joined, andother variable factors.

The work holder As'men'ti'oned previously a workpiece-supporting table14 is provided, and where irregularly shaped pieces are to be joined itis desirable to provide a positioning jig. In the embodiment illustratedin Figures 3 and 4, the

workpiece is in the form of a cork composition gasket for positioningthe pieces in proper alignment at each joint. Each of these guidescomprises a piece of insulation material 88 of dielectric propertiesadequate to withstand repeated operation within the high-frequency fieldand the temperature elevation created therein, such as Tefloninsulation. Each guide piece 88 overlies the electrode strip 34 and thepolystyrene facing member 35 and is secured to the base plate 86 and thefacing member 35 by screws 89 and 90 which pass through openings in theguide piece 88 and are received within threaded openings in the baseplate and facing member. This guide piece 88 projects above the surfaceof the electrode strip 34 a distance about equal to the thickness of theworkpiece being operated upon. A second guide piece 91 similar to guidepiece 88 is mounted in spaced relationship thereto on the lowerelectrode assembly, the spacing being such that the gasket segments maybe positioned between the guide pieces and held in such position byfrictional engagement therewith. Screws 92 hold the guide piece 91 inposition on the facing member 35.

Operation of the machine In the operation of the device, the oscillator6 is connected to a source of energizing voltage, and cylinder andpiston arrangement 13 is connected to air source S. Gasket segments tobe joined have previously been coated on their edges which are to bejoined with an adhesive such as a conventional phenolic resin adhesivedesigned for dielectric curing. The adhesive is preferably applied to astack of the segments and dried. All edges to be joined are preferablyadhesive coated.

The operator inserts an end piece 81 (Figure 3) into the jig where it isfrictionally held. The dried adhesive coated edges of the piece 81 willlie about midway longitudinally of the electrode strips 34 which, asnoted in Figure 6, are substantially longer than the joint to be made.This provides adequate electrode surface for bonding gaskets ofdifferent sizes from strips of difierent widths. After gasket segment 81has been positioned, the operator brings the adhesive-coated edges ofsegments 82 and 83 into abutting relationship with the adhesivecoatededges of segment 81, holding the segments 82 and 83 in his hands andpressing them toward segment 81 to bring the parts into firm engagement.The air cylinder and piston arrangement is then actuated, as by movementof a foot-controlled valve pressed by the operator, and this procedurebrings the crosshead and the associated upper electrode assemblies fromthe position shown in Figure 3 to the position shown in Figure 4 and inmore detail in Figure 7. In this position the upper electrode 17overlies the gasket segments at the adhesivecoated joint, and the piecesare confined at the joint between electrodes 17 and 34 and edge guides88 and 91 of the positioning jig. No substantial pressure needs to beapplied to the segments vertically at the joints, but good contactshould be maintained by pressure applied by hand by the operator.

As the crosshead 25 is lowered, the plates 23 of air switches" 9 and 10pass between plates 48 and 49 (Figure 7) and thus electrode strip 17 iscapacitively coupled to the high-frequency source. Switch 80 (Figure l)which controls the oscillator is actuated upon lowering of thecrosshead, and a high-frequency voltage is applied to the electrodesthrough the coaxial cables 11 and 12 and the air switches 9 and 10. Forjoining the gasket segments as shown a 200 megacycle, 150 watt, cyclicduty oscillator may be employed. Preferably the electrical controlcircuit for the system includes a timing mechanism which controls theduration of the heating cycle. For instance, this may provide a cycle ofa few seconds when the high-frequency field is applied to the glue linesto activate them, a few seconds dwell time after interruption ordiscontinuance of the field application for the adhesive to set whilethe parts are confined, and then an 6 automatic elevation of thecrosshead 25 for the removal of the joined workpiece.

Upon completion of these operations, if an end piece is to be applied tothe opposite ends of segments 82 and 83, such end piece will be insertedin the jig in the same manner as end piece 81, the opposite ends ofsegments 82 and 83 will be brought into abutting relationship with thenew end piece, and the operation will be repeated, thus forming acomplete gasket.

I claim:

1. In a device of the type described, the combination of a fixedelectrode, a movable electrode spaced from the fixed electrode, meansfor moving said movable electrode relative to said fixed electrode froman inoperative position to an operative position embracing a workpiecedisposed therebetween and constituting a load to be heated, meansdirectly connecting said fixed electrode to one side of a source ofhigh-frequency alternating electric voltage, and means carried by saidmovable electrode and effective upon movement from said inoperative tosaid operative position to closely capacitively couple said electrode tothe other side of said high-frequency source with negligible impedancein said coupling, said last named means comprising an air switch thecapacity of which is substantially greater than the capacity of the loaddisposed between said electrodes and including a fixed metal plateconnected to said high-frequency source and a metal plate connected tosaid movable electrode for disposition in effective capacitive couplingrelationship with said fixed metal plate upon movement of said movableelectrode to said operative position to provide a system in whichsubstantially all available voltage from said high-frequency source willbe developed within said workpiece.

2. In a device of the type described, the combination of a fixedelectrode, a movable electrode spaced from the fixed electrode, meansfor moving said movable electrode relative to said fixed electrode froman inoperative position to an operative position embracing a workpiecedisposed therebetween, means directly connecting said fixed electrode toone side of a source of high-frequency alternating electric voltageabove ground potential, and an air switch for coupling said movableelectrode to said high-frequency source comprising a pair of fixed metalplates connected to said high-frequency source at substantially groundpotential and a single metal plate connected to said movable electrodefor disposition in effective capacitive coupling relationship betweensaid fixed metal plates upon movement of said movable electrode to saidoperative position to closely couple said movable electrode to saidhigh-frequency source.

3. In a device of the type described, the combination of a pair of fixedelectrodes disposed in spaced relationship, a pair of movable electrodesdisposed in spaced relationship complementary to said fixed electrodes,means for moving said movable electrodes relative to said fixedelectrodes from an inoperative position to an operative positionembracing a workpiece disposed between said spaced complementaryelectrodes, a coaxial cable connecting said pairs of electrodes to asource of high-frequency alternating electric voltage, the shield ofsaid cable being at ground potential and the inner conductor of saidcable being at a potential above ground, said conductor being connectedto said fixed electrodes and said shield being connected to said movableelectrodes by a pair of air switches substantially at ground potential,each switch comprising spaced metal condenser plates movable withrespect to one another, means connecting one of said condenser plates toeach of said movable electrodes, and means guiding said moving means forsaid movable electrodes to bring said condenser plates into efiectivecapacitive coupling relationship coincident with movement of saidmovable electrodes into operative position with respect to saidworkpiece.

4. In a device of the type described, the combination of claim 1 inwhich there are a pair of movable electrodes and a pair of fixedelectrodes with a crosshead connecting the movable electrodes and 'inwhich said stationaryelectrodes are connected to said source aboveground potential and said movable electrodes are capacitively coupled by.two of said air switches to the other side of said source at groundpotential.

5. In adevice of the type described, the combination of a fixedelectrode positioned upon a mounting plate of dielectric material, amovable electrode displaceable with respect to said fixed electrode froman inoperative position to an operative position embracing a workpiecedisposed therebetween, a capacitive coupling device for coupling saidmovable electrode to a source of high-frequency alternating electricvoltage at substantially ground potential comprising a fixed metal plateand a movable metal plate electrically connected to said movableelectrode, a connector plate electrically connected to said fixed plateand :to saidhigh-frequency source, aninsulating spacing plate-interposedbetween said connector plate and an insulating backing plate for saidfixed electrode, fastening means for said backing plate received within8 said spacing plate, fasteningmeans for said spacing plate receivedwithin said connecting plate, and means disposed in :spaced relationshipto said connecting plate connecting said stationary electrode to saidsource at a potential above ground.

References Cited in the file of this patent UNITED STATES PATENTS2,109,323 Smith Feb. 22, 1938 2,288,268 Crandell June 30, 1942 2,467,782Schuman Apr. 19, 1949 2,474,420 'Himmel June 28, 1949 2,504,956 AtwoodApr. 25, 1950 2,504,969 Ellsworth Apr. 25, 1950 2,516,324 Joy July 25,1950 2,522,487 Warren Sept. 12, 1950 2,572,226 'Walstrom Oct. 23, 1951FOREIGN PATENTS 556,292 Great Britain Sept. 28, 1943

